The advent of the computer has already had a profound effect upon human society, and the impact of processing technology is expected to increase. Indeed, the desirability to store information for subsequent retrieval currently grows at an exponential rate. Thus, various types of devices have been developed to store data both for on-line usage as well as for archival purposes.
Where on-line processing requires data to be readily at hand, a significant improvement was provided by the advent of the magnetic disk storage array. Here, one or more magnetic disks are provided, and a read/write recording head is used to record information on the disk as well as to retrieve information or data for use by the computer processor. Significant strides have been made in the ability to increase the density of data stored on such magnetic disk arrays. In order to gain an even higher density for on-line data, the optical disk was developed. These devices record data based upon a very small wavelength of light so that a higher density is obtained due to this technique. Laser light is employed to read the stored information or data on the optical disk.
In early days of the computer, before the advent of the magnetic disks and the optical disk storage assemblies, data was typically stored on magnetic tapes, such as reel-to-reel tapes and later cassettes. In a magnetic tape storage device, a magnetic coil is used as a transducer both to imprint data magnetically on a moving band of magnetic film; thereafter, when the film is advanced across the transducer, the data may be read and re-input into a co-processor. Magnetic tape can be erased and rewritten many times and has an advantage of low cost.
Magnetic tape is still a highly desirable format for archiving data for rapid access is of less significance and cost is of concern. However, where vast quantities of data are to be maintained, these tapes can be bulky due to the physical number necessary to store the quantity of data. The capacity for such tapes to store data, of course, is dependent upon the number of “tracks” which can be independently placed across the width of the tape.
The ability to write data rapidly onto a magnetic tape film and the accessibility of data to be read from the film is a function of two variables: (1) the density of storage; and (2) the speed at which the tape medium may be transported across and accurately written/read by the transducer. Thus, for example, a magnetic tape read/write system that is able to read and write nine tracks of data on a single strip of tape will hold four and one-half times the amount of data as a system which only utilizes two tracks.
Therefore, efforts to increase the capacity of magnetic tapes to store data have included substantial efforts to increase the number of tracks which can be written on a band of magnetic tape. In the beginning, the speeds associated with the transfer of tape between the storage reel and the take-up reel were relatively slow. The registration of the edges of the tape layers to form the opposite surfaces of the tape pack was not especially critical. Often, the edges of consecutive layers of the tape might be slightly off-set from one another or “stagger-wrapped”. In more recent times, the speed of wrapping or winding a tape onto either the storage reel or the take-up reel has increased dramatically. This is especially true in the electronic information storage arena wherein magnetic tape, or “film” or optical tape is used to store data, both for on-line usage as well as for archival purposes.
In the above-described systems, storage reels of tape, whether flanged or flange-less (for example as used in cartridges) may be placed on the machine during use. A threading assembly engages the free end of the tape and passes it through the machine. Typically, the tape is threaded across air bearings, past the transducer and into a take-up hub or reel. The length of the tape is then passed through the machine so that information may be placed on the tape or retrieved therefrom. During this process, the length of tape is transferred onto a take-up reel or hub that is either a part of the machine itself, included within the cartridge or that is mounted and de-mounted from such machine. After being transported through the machine, the tape may be rewound onto the storage reel and removed from the machine.
As was explained in my earlier U.S. Pat. No. 5,777,823, issued Jul. 7, 1998, it is important that the lateral edge of the tape moving in a transport direction be properly registered along a reference plane, called the datum, so that the data may be accurately input and retrieved from the tape medium. Support of the tape during transport is therefore critical, and typically employs guide rollers, air bearing and the like as is known in the art. Improved air bearings are the subject of U.S. Pat. No. 5,777,823 and U.S. patent application Ser. No. 10/111,728 filed Apr. 26, 2002 (priority date Oct. 28, 1999), the disclosures of which are hereby incorporated by reference. It is also important that the read/write head be accurately positionable. A representative structure for such positioning is shown in U.S. Pat. No. 6,078,478, the disclosure of which is hereby incorporated by reference.
Take-up reels are typically constructed to have a central hub that has annular flanges and a width slightly greater than the width of the tape. It is also known to use flange-less hubs in winding tape media. In either case, the hub is rotated about a central winding axis, and the length of tape is wrapped circumferentially around the hub. Such winding results in a tape pack as successive layers of tape build in a radial direction. The edges of the tape generally define a pair of oppositely disposed surfaces generally along planes that are perpendicular to the winding axis. The width of the tape pack is thus defined by the distance between these two planes. The flanges of a flanged reel are intended to protect the tape pack.
As tape transport speeds have increased, a problem has evolved which is interchangeably called “scatterwind” or “stagger-wrap”. Where tape is wound at high speed onto a hub, the tape entrains air. That is, air within the boundary of air adjacent to the tape moves into the tape pack and becomes entrapped between the advancing layer and those layers already on the tape pack. Some of this converging wedge of air is laterally displaced at the “nip” which is the point of tangency between the film pack and the incoming (or outgoing) layer of tape. When the tape pack is subsequently brought to rest, the spiral-air bearing is ejected so as to decrease the pack's radius until all adjacent tape layers have come into direct contact. As this occurs, the layers may shift laterally with respect to one another resulting in a tape pack that has a significant amount of stagger wrap. Stagger-wrap presents a problem to the industry where the alignment of the lateral edge of the tape is critical with the read/write transducer. If a tape pack has a significant amount of stagger wrap, the perturbation of this stagger wrap propagates through the advancing tape layer as it is played off of the reel or hub. This causes potential error in either reading or writing the data. Therefore, it is desirable to eliminate the misregistration of the layers forming the tape pack by guiding the registration of the incoming tape layer as it winds onto the hub. The problem of “stagger-wrap” was addressed in U.S. patent application Ser. No. 09/614,575 filed Jul. 12, 2000.
Many tape drives utilize a cartridge which may be mounted or de mounted into the recording and reading apparatus. These cartridges typically contain a spool of tape media upon which information may be stored. The tape media is then transported across the read/write recording head either to place data on a blank tape which you override existing data, as is the case with a “write” operation or, alternatively, to retrieve information that already exist on the tape media during the “read” state. In either case, the tape is typically attached to a connector that either forms a leader block or that is adapted to be engaged by a leader block that is part of the drive mechanism. The drive mechanism engages the free end of the tape by means of the leader block, and mechanically threads the tape across air bearings that ore disposed on either side of read/write recording head. The drive mechanism conveys the leader block to a take-up hub that, typically, is constructed to have a central hub with annual flanges at a width slightly greater than the width of the tape. However, it is known to use flange-less hubs in winding tape media. In either case, the hub is rotated about a central winding axis, and the link of tape is wrapped circumferentially around the hub. Such winding results in a tape pack of successes layers of tape build in radial direction. The flanges of a flanged reel are intended to protect the tapes pack.
As a result of the increasing speeds of winding tape, is important that the tape be wound smoothly and uniformly into the tape pack. Even slight variations in the radius of winding can result in eccentricities of the tape pack. Such eccentricities cause at least two problems. On one hand, if there are small variations in the hub surface or in the resulting tape pack, significant damage to the tape may result with this damage repeating itself over many wraps. Any damage to the tape, of course, can effect the integrity of data that is stored on the tape. In addition, tension variations may occur since the radius of the tape pack itself changes for an instance where the radius is not perfectly uniform. Tension variations effect the tape's stability and decrease the read/write performance of the drive. These tension variations can also create stresses in the tape due to repeated tension cycling. Each of these problems becomes increasingly significant as track density increases.
In one type of threading and take-up assembly, the leader block is shaped so it can fill an opening left in the take-up reel hub, providing a smooth surface upon which the tape must be wound. The primary drawback of this system is that the leader block must be sized according to the gap in the hub and have tolerances that match the hub diameter. In those systems wherein each storage cartridge has its own leader block, there is always some variation, cartridge to cartridge, in the sizing of such leader blocks. These variations result in non-uniformities in the hub diameter when the leader block is mounted in the recess of the hub. Accordingly, the undesired variations in uniformity of the tape pack result.
Where cartridges do not have an integral leader block, such as the case where the tape transport mechanism has its own leader block that engages the free end of the tape, limitations still result. Even though having a leader block as part of the tape drive apparatus improves the tolerance situation, the existing design for most common tape leader pins make it necessary to attach the tape on one side of the leader block because the end must be smooth to match the hub. This creates a need for complex mechanisms to pick the tape. Also, the wind direction of the take-up reel determines which side of the leader block the tape must lay on, which forces the tape to be picked from the corresponding side of the leader block. Otherwise, the tape tension will apply a pull out force on leader block when it is in the take-up hub.
One attempt to address this problem with an internal leader block is described in U.S. Pat. No. 5,979,813 issued Nov. 9, 1999 to Mansbridge et al. In Mansbridge, a take-up hub is provided with a take-up hub having a curve surface portion and a flat mounting area. A leader block is then provided that mounts onto the flat area of the take-up hub and completes the surface in an attempt to provide a smooth, cylindrical winding surface for the tape pack. In essence, the take-up hub, then, has a removed section that forms a leader block, with the take-up hub than having a leader block receiver section that is configured to receive and position the leader block while is connected to the tape to form the continually uniform curve surface.
Despite the advancements set forth in the '813 patent, there remains a need to provide an assembly that will allow the tape picker or tape leader block to be a virtually any configuration. There is a further need to have a system that can be used with a tape picker or a tape leader block that can accommodate manufacturing tolerances. There is a further need to provide a take-up reel structure that allows the tape to be wound in opposite angular directions, and that is independent of the tape picker or leader block design. The present invention is directed to meeting these needs.